A series of tremors that began near Puget Sound and moved south appears to have finally stopped.
The Pacific Northwest Seismic Network reports that the episodic tremor slip, which is a fairly common seismological phenomenon in some subduction zones, ended southwest of Eugene, Ore. after more than a month.
The last tremor was recorded on March 1.
“…thus, after a couple of days with no more tremors, I declare this one is over,” the Seismic Network wrote on its blog.
The tremors ended a few days later than expected. It covered much of the same area as a previous event.
An episodic tremor slip, or slow slip, can last for minutes to days, even weeks, according to a spokesperson with the Seismic Network. They generate such low levels of shaking that only sensitive instruments can detect them. Slow slip episodes have been occurring about every 14 months since the 1990s in northern Washington and British Columbia, according to the Seismic Network.
The latest slip began around the beginning of February. It is unclear if it was the same slip as one that began in December of 2015. However, the Seismic Network reports the slip that began near Vancouver Island ended Jan. 16, and the latest began Jan. 20 in Southern Washington.